The role of sediment supply in esker formation and ice tunnel evolution

Burke, Matthew J.; Brennand, Tracy A.; Sjogren, Darren

doi:10.1016/j.quascirev.2015.02.017

Cited by 29 publications

(62 citation statements)

References 50 publications

(135 reference statements)

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“…Discontinuous sub‐horizontal and wavy reflectors, in places dipping gently southwards, with a hummocky upper surface that mimics the underlying reflectors (RF5), can be identified in line 155. These are consistent with ridge‐scale sediment macroforms associated with a dynamic depositional environment (Brennand, ; Burke et al, ). The dip direction of some reflectors in this zone is opposite to the general northwards drainage trend, indicating that these are shallow backsets related to headward accretion on the stoss‐side of the sediment macroform in a channel (e.g.…”

Section: Results and Interpretationsupporting

confidence: 82%

“…The RF5 hummocky reflectors (e.g. Figure C, lower panel), also found at Carlatton Farm (Figure D), are consistent with ridge‐scale esker macroforms (Brennand, ; Burke et al, ). The discontinuous dipping reflectors that overlay the hummocky surface are interpreted as foresets (Russell et al, ; Woodward and Burke, ; Clayton et al, ; Winsemann et al, ), indicating north‐west drainage and sediment progradation into a water body based on the orientation of dip.…”

Section: Results and Interpretationsupporting

confidence: 66%

“…RF7 in Figure C) that are interpreted as potential evidence of deformation due to removal of lateral ice support leading to sediment collapse (e.g. Holmes, ; Fiore et al, ; Johnson and Clayton, ; Clayton et al, ; Burke et al, ).…”

Section: Results and Interpretationmentioning

confidence: 99%

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Complex kame belt morphology, stratigraphy and architecture

Lovell

Livingstone

Boston

et al. 2019

Earth Surf Processes Landf

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The development of glacier karst at the margins of melting ice sheets produces complex glaciofluvial sediment‐landform assemblages that provide information on ice sheet downwasting processes. We present the first combined geomorphological, sedimentological and geophysical investigation of the Brampton Kame Belt, an important glaciofluvial depositional zone at the centre of the last British‐Irish Ice Sheet. Ground‐penetrating radar (GPR) data allow the broad scale internal architecture of ridges (eskers) and flat‐topped hills (ice‐walled lake plains) to be determined at four sites. In combination with sediment exposures, these provide information on lateral and vertical variations in accretion styles, depositional boundaries, and grain size changes. Building on existing work on the subject, we propose a refined model for the formation of ice‐walled lake plains resulting from the evolution and collapse of major drainage axes into lakes as stable glacier karst develops during deglaciation. The internal structure of esker ridges demonstrates variations in sedimentation that can be linked to differences in ridge morphologies across the kame belt. This includes low energy flow conditions and multiple accretion phases identified within large S‐N oriented esker ridges; and fluctuating water pressures, hyperconcentrated flows, and significant deformation within a fragmented SW–NE oriented esker ridge. In combination with updated geomorphological mapping, this work allows us to identify two main styles of drainage within the kame belt: (1) major drainage axes aligned broadly S‐N that extend through the entire kame belt and collapsed into a chain of ice‐walled lakes; and (2) a series of smaller, fragmented SW–NE aligned esker ridges that represent ice‐marginal drainage as the ice sheet receded south‐eastwards up the Vale of Eden. Our study demonstrates the importance of integrated geomorphological, sedimentological and geophysical investigations in order to understand complex and polyphase glaciofluvial sediment‐landform assemblages. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

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Section: Results and Interpretationsupporting

confidence: 82%

Section: Results and Interpretationsupporting

confidence: 66%

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Complex kame belt morphology, stratigraphy and architecture

Lovell

Livingstone

Boston

et al. 2019

Earth Surf Processes Landf

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“…The modeled dynamics of the sediment‐bearing R‐channel fed by fluctuating water input produced simulated sedimentary deposits (Figure ) that closely match those observed in esker ridges in southern Alberta (Burke et al, ). In our simulations the sediment pulses occur because of temporary sediment accumulation, although the mechanisms that could produce sediment pulses discussed in the previous section would also lead to these deposits.…”

Section: Discussionmentioning

confidence: 99%

Modeling Sediment Transport in Ice‐Walled Subglacial Channels and Its Implications for Esker Formation and Proglacial Sediment Yields

2018

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Sediment yields from glacierized basins are used to quantify erosion rates on seasonal to decadal timescales as well as conditions at the glacier bed, and eskers hold valuable information about past subglacial hydraulic conditions in their spatial organization, geometry, and sedimentary structures. Ultimately, eskers are a record of past glacio‐fluvial sediment transport, but there is currently no physical model for this process. We develop a 1‐D model of morphodynamics in semicircular bedrock‐floored subglacial channels. We adapt a sediment conservation law developed for mixed alluvial‐bedrock conditions to subglacial channels. Channel evolution is a function of melt opening by viscous heat dissipation from flowing water and creep closure of the overlying ice, to which we add the closure or enlargement due to sediment deposition or removal, respectively. We apply the model to an idealized land‐terminating glacier and find that temporary sediment accumulation in the vicinity of the terminus, or the formation of an incipient esker, is inherent to the dynamics of the channelized water flow. The alluviation of the bed combined with the pressurized channel flow produces unexpected patterns of sediment evacuation: We show that the direction of hysteresis between sediment and water discharge is not necessarily linked to a supply‐ or transport‐limited system, as has been hypothesized for proglacial sediment yields. We also find that the deposition of an incipient esker is a function of a compromise between water discharge and sediment supply, but perhaps more importantly, ice‐surface slope and the temporal pattern of water delivery to the bed.

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“…A more detailed consideration of different sediment sizes would allow for greater comparison with existing geological studies of eskers (e.g., Burke et al, 2015;Cummings et al, 2011), but this is beyond the scope of the current model. We have also assumed a single grain size (sand) that is easily mobilized, and our results may not apply to much larger sediments such as boulders.…”

Section: Limitations and Extensionsmentioning

confidence: 99%

A Model for the Formation of Eskers

Hewitt

Creyts

2019

Geophysical Research Letters

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We develop a mathematical model for esker formation by the continuous deposition of sediments near the mouth of water‐filled subglacial tunnels. We assume a retreating ice sheet margin and prescribe meltwater and sediment supply to a channelized subglacial drainage system. The hydrodynamic model for the subglacial channel has its cross section governed by wall melting, creep closure, and sediment deposition. Sediment‐carrying capacity typically increases downstream, before decreasing rapidly near the margin, suggesting that most deposition occurs there. This can lead to “choking” near the margin, which is offset by enhanced melting to keep the channel open. The model shows that the deposition rate varies roughly quadratically with sediment supply and inversely with water flux. For given sediment supply, the model suggests esker formation is most prevalent in smaller channels. Larger ice sheet melt rates likely produce more closely spaced eskers, but with smaller cross sections.

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The role of sediment supply in esker formation and ice tunnel evolution

Cited by 29 publications

References 50 publications

Complex kame belt morphology, stratigraphy and architecture

Complex kame belt morphology, stratigraphy and architecture

Modeling Sediment Transport in Ice‐Walled Subglacial Channels and Its Implications for Esker Formation and Proglacial Sediment Yields

A Model for the Formation of Eskers

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